1. Field of the Invention
This invention relates to a system for controlling power to multiple AC lighting loads from both local controls and a central location.
2. Description of the Related Art
Systems are known for controlling lighting loads from both a master control and from local controls that are near the loads.
Remote control master switching systems are available from General Electric. These systems include master selector switches to provide individual local control or master control. A similar system is available from Touch-Plate International, Inc., of Emeryville, Calif.
Centrally-controlled dimming systems are available from LiteTouch, Inc. and from Electro Controls Inc., both of Salt Lake City, Utah.
The Touch-Plate, LiteTouch, and Electro Controls master control systems all use a remote power control panel that contains triacs and relays to control (i.e., to dim or switch) the power to the load. The controls for the system include a centrally located master station and, dispersed throughout a building, buttons to turn the lights on and off or to provide "raise/lower" dimming of the lights. Raise/lower dimming is accomplished by pushing a button to raise or lower the power to the lighting load. When the desired level is reached, the button is released.
Another system for central dimming of lighting is available from Lightolier Controls, Secaucus, N.J. That system involves multiple local ("Easyset") controls that can provide raise/lower dimming. Multiple Easyset dimmers can be operated through a single master; however, they must all be on the same circuit, which, in accordance with the National Electrical Code, limits total power to 2000 W.
The Grafik Eye.RTM. dimming control, manufactured by Lutron Electronics, Coopersburg, Pa., allows a number of lighting loads to be controlled from a central location. The power delivered to each load can be set by adjusting a corresponding actuator, or by selecting among four preset "lighting scenes", each scene corresponding to specific power levels delivered to each load. The system also includes auxiliary scene-select controls, which can be located throughout an area, to enable a user to select lighting scenes from additional locations.
Lutron also provides central dimming and switching control of multiple zones of lighting with Versaplex.RTM. and Aurora.RTM. dimming systems. These systems do not include wallbox dimmers dispersed to the spaces in which lighting is being controlled, instead requiring centralized power cabinets.
A system available from Enercon Data Corp., of Minneapolis, Minn., uses power relays, which can be mounted in junction boxes, throughout a building and can be locally or centrally switched. In order to dim an area with this system, a standard dimmer may be located near the load; however, the enabling switch that turns power to the dimmer on and off must be separated from the dimmer by a physical barrier (for reasons discussed below). As a result, separate dimmers and switches are required, increasing the number of controls on the wall and complicating the wiring.
Another system, available from X-10 (USA) Inc., of Northvale, N.J., allows master control of a number of local controls wired throughout a house or other building. The X-10.RTM. Powerhouse.TM. system uses the existing powerline carrier to send control signals to each of the local controls. The local controls interpret the signals and switch a power relay or adjust the power output of a dimmer accordingly. The system may independently control up to eight local controls and has the added capability to turn all the local controls on or off simultaneously.
A wallbox dimmer with plural remote control switches is disclosed in U.S. Pat. No. 4,563,592, issued Jan. 7, 1986, to Yuhasz et al, incorporated herein by reference. The system allows dimming of a lighting load from a central location, and toggle on/off control from a plurality of remote locations. Additionally, the system discloses a master control system, whereby a number of dimming controls can be simultaneously toggled from a master toggle switch.
It is well known in the art to use manually operable multi-pole power switches (e.g., three-way and four-way toggle switches) to turn a lighting load on or off from a plurality of locations. Such a system typically includes two three-way switches, connected in series between incoming hot and the lighting load, and any number of four-way switches wired between the two three-way switches. Toggling any one of the switches causes the light output to change states, (i.e. to change from on to off or vice versa). One drawback of these systems is that toggling a switch to a certain position does not consistently correspond to the same status of the lights, either on or off. This can be a problem if, for instance, the light cannot be seen from the switch location (as is often the case with outdoor lighting that is controlled from within a house), because the user does not know if he is turning the lights on or off. The present invention provides electrically-operable three-way switches, which are better adapted for remote or light-touch operation and which permit greater design flexibility to meet aesthetic requirements.